High-Temperature Anion-Exchange Membrane Fuel Cells

Abstract

In the past few years, developments in anion-exchange membranes (AEMs) have led to a significant increase in hydroxide conductivities, ultimately yielding striking improvements in the performance of anion-exchange membrane fuel cells (AEMFCs) at low operating temperatures, usually at 40-80 oC. Aside from these remarkable achievements, the literature was void of any work on AEMFCs operated at temperatures above 100 oC, despite the consensus from various models remarking that working at higher cell temperatures may lead to many significant advantages.1 Herein, we present the first results of high-temperature AEMFCs (HT-AEMFCs) tested at temperatures above 100 oC. The first LDPE AEM tested at 110 oC exhibited a true hydroxide conductivity close to 300 mS cm-1, the highest hydroxide conductivity ever measured for an AEM. Based on this membrane, a non-optimized AEMFC with Pt-based electrodes was tested also at 110 oC with H2/O2 delivering a peak power density of 2.1 W cm-2 (measured at 0.51 V), reaching a limiting current of above 6 A cm-2. The cell boasted a current density of as high as 574 mA cm-2 measured at 0.8 V, rivaling other AEMFCs reported in the literature. Furthermore, the AEMFC retained 0.8 V performance after 50 h of operation at a constant current density of 200 mA cm-2.2 The second ETFE AEM tested at 105 oC maintained a true OH‾ conductivity of 201 mS cm-1. The HT-AEMFC based on this membrane contained a critical raw material (CRM)-free N-doped-C cathode and delivered a peak power density of 1.14 W cm-2 while reaching a limiting current density of 2.9 A cm-2, with realization of a reduced cell resistance at 105 oC compared to tests performed at 60 and 80 oC.3 These very first results obtained at temperatures above 100 oC represent a significant landmark for the research and development of fuel cell technology, opening a wide door for a new field of research on HT-AEMFCs.(1) Dekel, D. R. Review of Cell Performance in Anion Exchange Membrane Fuel Cells. J. Power Sources 2018, 375, 158–169. https://doi.org/10.1016/j.jpowsour.2017.07.117.(2) Douglin, J. C.; Varcoe, J. R.; Dekel, D. R. A High-Temperature Anion-Exchange Membrane Fuel Cell. J. Power Sources Adv. 2020, 5, 100023. https://doi.org/10.1016/j.powera.2020.100023.(3) Douglin, J. C.; Singh, R. K.; Haj, S.; Li, S.; Biemolt, J.; Yan, N.; Varcoe, J. R.; Rothenberg, G.; Dekel, D. A High-Temperature Anion-Exchange Membrane Fuel Cell with a Critical Raw Material-Free Cathode. Submitted to Chem. Eng. J. Adv. 2021.